GDAL driver ensure_registered should check counts separately

[Matthew Somerville]

It is possible for external code to register some of the drivers, and then Django code will die because it expects them all to have been registered. For example, on a standard Debian box (wheezy or jessie), the following code works fine:

from django.contrib.gis.gdal import DataSource
ds = DataSource('/home/matthew/data.shp')

whilst the following code dies saying the file could not be loaded:

from osgeo import gdal
from django.contrib.gis.gdal import DataSource
ds = DataSource('/home/matthew/data.shp')

This is because the osgeo import has registered the raster drivers, but not the data source ones, and yet Django's ensure_registered will only try and register both if the overall count is zero.

[Tim Graham <timograham@…>]

In fb951fb0:

Fixed #27103 -- Registered vcapi/rcapi GDAL prototypes based on their own drivers.